Transmission and brake bands now in use are made substantially entirely of steel components with the usual friction lining material secured to the inner surface. The manufacture of steel brake bands requires numerous operations, including welding and mechanical fastening, both in the fabrication of the components and in the final assembly.
The friction band of the present invention is made of a length or strap of filament-reinforced composite material containing a plurality of long-strand, continuous filaments of glass or the like embedded or encapsulated in a resinous plastic material matrix such as epoxy. Preferably the ends of the filament-reinforced composite band are doubled over the apply and reaction lugs, providing a strong connection in which the load transfer from the lugs to the band is evenly distributed. In conventional designs, the load is transmitted through welds or rivets which constitute weak points.
The band is manufactured by curing the plastic matrix while wrapped around a cylindrical mandrel to provide its final shape, at the same time maintaining the filaments in tension so that in the final product the filaments are straight and parallel to one another. If the filaments are not held in tension during molding, they tend to transmit forces unevenly when the band is in service, with the possibility of cracking the plastic matrix of the band and causing transverse separation.
Preferably a length of fibrous reinforcing material is interposed between the composite band and the friction lining. The reinforcing material further strengthens the band, especially in a transverse direction.
It has been found that during molding, the plastic matrix becomes flowable or liquid as its temperature rises to the necessary curing temperature, and the plastic run-off may get on the friction lining, which, of course, is undesirable. However, the fibrous reinforcing material has the ability to soak up or absorb the run-off. The plastic which is absorbed by and impregnated into the fibrous reinforcing material has the advantage of further strenthening the latter.